Currently, an electric device such as a non-aqueous electrolyte secondary battery including a lithium ion secondary battery, which is used for a mobile device such as a mobile phone, is available as a commercial product. Among those, the non-aqueous electrolyte secondary battery generally has a constitution that a positive electrode having a positive electrode active material or the like coated on a current collector and a negative electrode having a negative electrode active material or the like coated on a current collector are connected to each other via an electrolyte layer in which a non-aqueous electrolyte solution or a non-aqueous electrolyte gel is maintained within a separator. According to absorption and desorption of ions such as lithium ions on an electrode active material, charge and discharge reactions of a battery occur.
In recent years, it is desired to reduce the amount of carbon dioxide in order to cope with the global warming. As such, a non-aqueous electrolyte secondary battery having small environmental burden has been used not only for a mobile device or the like but also for a power source device of an electrically driven vehicle such as a hybrid vehicle (HEV), an electric vehicle (EV), and a fuel cell vehicle.
A non-aqueous electrolyte secondary battery which is hopefully to be applied for an electrically driven vehicle is required to have high output and high capacity. As a positive electrode active material which is used for a positive electrode of a non-aqueous electrolyte secondary battery for an electrically driven vehicle, a lithium cobalt composite oxide as a layered composite oxide has been already widely used as it enables obtainment of high voltage at 4 V level and also has high energy density. However, cobalt as a raw material of the composite oxide is a naturally limited resource with high price, and thus considering the possibility of having a highly increasing demand in future, it is unstable in terms of raw material supply. Furthermore, there is a possibility of having increased cost for the raw cobalt material. Accordingly, it is desired to have composite oxide having less cobalt content.
Like the lithium cobalt composite oxide, a lithium nickel composite oxide has a layered structure and it is relatively inexpensive compared to lithium cobalt composite oxide. Furthermore, it is comparable to the lithium cobalt composite oxide in terms of theoretical discharge capacity. From this point of view, it is expected that the lithium nickel composite oxide is used for constituting a battery with practically useful high capacity.
In a lithium ion secondary battery in which a composite oxide containing lithium and nickel (hereinbelow, also simply referred to as “lithium nickel-based composite oxide”) like lithium nickel composite oxide is used as a positive electrode active material, charge and discharge is carried out according to desorption and insertion of lithium ions in the corresponding composite oxide.
Herein, in order to use a lithium ion secondary battery as a power source for driving a vehicle or the like, not only the high capacity but also the high output, which determines acceleration performance or the like, is required. Furthermore, to respond to a use for a long period of time, it is required for the battery to have a long service life. In response to such requirement, in JP 2011-54334 A, a technique of using in combination lithium transition metal composite oxide with layered crystal structure containing manganese and nickel which can insert and release lithium ion and lithium transition metal composite oxide of spinel crystal structure which contains manganese as a positive electrode active material is disclosed. Furthermore, according to the technique disclosed in JP 2011-54334 A, the aforementioned problem is to be solved by having 50% or more (in molar ratio) of the composition ratio of nickel relative to the transition metal element other than lithium that is contained in the lithium transition metal composite oxide of layered crystal structure.